We’ve all heard the term “One bad apple spoils the whole bunch.”

Unfortunately, this is especially true when it comes to employees.

It only takes one disgruntled employee to lower the tone at work, and if left unchecked, to bring down the whole company in a short amount of time.

“We engage in emotional contagion,” says Sigal Barsade, a management professor who studies the influence of emotions on the workplace. “Emotions travel from person to person like a virus.”

Taking some time to educate yourself on harmful employee behavior can help you to spot a problem worker as soon as issues arise. Knowing what to look for will help you to keep your business going strong, and allow you to curb potentially harmful behavior before it gets out of hand.

Here are five problem employees that you’ll want to watch out for.

1.The Busybody

We all know someone like this. Busy bodies are not as productive as their name makes them seem. This type of worker is very involved with everyone else’s business, usually to the point of neglecting their own. They’re also constantly on the lookout for other employees who may be doing something wrong. This type of behavior can be extremely disruptive, causing stress and friction in the workplace and derailing production.

2.The Constant Complainer

Often known as the Negative Nelly –this behavior can bring down a group of employees quicker than a monkey bringing down a bunch of bananas! Constant complainers are quick to point out problems with others or working conditions, but rarely, if ever, offer any solid solutions. They seem to thrive on roadblocks and halting production, constantly complaining but rarely helping.

3.The Bitter Apple

These are the ones that hold grudges. They don’t work well in teams and feel as though they are always the odd one out. They are bitter about the promotion they didn’t get or coworkers who received recognition. They disagree with just about everything and everyone, and their bitter attitude can have a negative impact on your other employees as well.

4.The Rebel

Rebellion is not limited to the teenage years. Some employees carry this attitude with them throughout life and find it difficult to get along with others. They hop from job to job, disrupting production and causing upheaval as they go –leaving a massive wreck in their wake as they move along. They pride themselves in, “Telling it how it is” when really, they are just trying to call the shots. When things don’t go their way they resist, and hold out for as long as possible. Letting this behavior go on can be toxic to your other employees and business as well.

5.The People Pleaser

The people pleaser is determined to please everyone, never says no, and always says yes to additional work that may be thrown their way. While this may sound like the ideal employee, this type of worker has problems all of their own. As you know, it’s impossible to please everyone, and trying to constantly make everyone happy will only wear this worker out. This employee is susceptible to resentment, and burnout and their work will usually suffer as a result. While the pleaser certainly isn’t the worst behavior in the group, it’s something you’ll want to watch out for with nonetheless. If you find a people pleaser make sure you help them channel some of their motivation into a worthwhile project where they won’t burn out trying to please everyone.

Once you spot harmful behavior, what can you do to stop it? The good news is that the sooner you take action, the greater your chance at stopping bad behavior before it escalates. Once you recognize an issue, it’s important to take your worker aside, and speak with them privately. Inform them that you noticed something was wrong, and see if there is any stress or underlying personal issues that could be causing the issue. Then, work with your employee to draw up solutions that you and they can work towards. This could be arranging flexible work hours for an overstressed worker who may be struggling to find a work-life balance or striving to implement positive changes that will help to improve working conditions.

Don’t give up on your worker just because you notice an issue. In many cases, a little bit of understanding, and guidance can go a long way towards helping you to come up with a solution. If, however, you notice repeated issues with an employee, it may be time to consider whether it’s time to take your discussions to the next level.